The present invention relates to a novel silicon-containing polymer and a novel photosensitive material containing siloxane linkages, which is a material for a resist having a photosensitive group responsive to electron rays, X-rays, UV light and deep UV light used when producing a semiconductor integrated circuit and which is also usable as a layer-insulation film or a protective film.
The silicon-containing polymers are used in a variety of fields for the reasons that they exhibit excellent heat resistance and cold resistance, that the electric characteristics thereof are stable over a wide range of temperature, and the like. Moreover, silicon-based polymers provided with photosensitive group have been developed recently and the uses are spreading out as electronic materials, too.
In the electronic field, particularly in the production of semiconductors (integrated circuits), the fine processing of substrates has become more complicated and higher precision has been requested as the high integration progresses. Accompanying with this, the technique for performing the fine processing on a scale of submicron on a substrate with differences in levels has become problematic and various methods have been contrived. As one of them, the two-layer resist technique used silicon-based resist as a top layer was proposed, which is particularly spotlighted recently. This technique will be explained.
A resin or resist having resistance to halogen gas is spin-coated onto bottom layer, which is subject to soft-or hard-baking. Then, a silicon-based resist is spin-coated onto the top layer. Using an exposure device, the top layer resist is exposed to light and only the top layer is developed. Then, making the pattern area of the top layer resist as a mask, the bottom layer resist is etched with O.sub.2 gas plasma. Finally, making the bottom layer resist as a mask, the substrate is etched with halogen gas.
The functions to be requested for the top layer resist are as follows:
(1) To be excellent in the resistance to O.sub.2 plasma. PA1 (2) To be excellent in the flatness. PA1 (3) To have high glass transition temperature. PA1 (4) To have high resolution. PA1 (5) To have high sensitivity.
The silicon-containing resist materials are excellent in the resistance to O.sub.2 plasma and some resist materials using them are known. As representatives, a method to attach a silyl group directly or indirectly to the benzene rings of Novolak resin or polystyrene, a method to utilize the polysilane linkage, and, in particular, recently, a method to utilize a ladder polymer (silsesquioxane linkage) are proposed.
In the case of the type with attached silyl group directly or indirectly to the benzene rings, however, a problem that the resistance to O.sub.2 plasma is insufficient exists because of that the content of Si is low and Si is introduced to a side chain. Moreover, in the case of polysilane type, poor coating property and stability are generally pointed out though the content of Si may be increased depending on the kind of compounds. Furthermore, in the case of silsesquioxane type polymers, there is a problem that the sensitivity is not enough though the resistance to O.sub.2 plasma is excellent.
As described above, it is the status quo that the resist materials being excellent in the resistance to O.sub.2 plasma and the flatness and having all of high Tg, high resolution and high sensitivity have not ever been developed.
The invention was made to dissolve the problems as above and the purpose thereof is to provide a novel silicon-containing polymer and a photosensitive material using the same, which is excellent in the resistance to O.sub.2 plasma and the flatness and which has high Tg, high resolution and high sensitivity.
As a result of diligent studies in such background, the inventors have found that, by using a polymer having a single siloxane cyclic compound as a repeating unit or a copolymer having various siloxane cyclic compounds as repeating units, a resist material being highly sensitive, highly flat and excellent in the resistance to O.sub.2 plasma and yet having high Tg can be obtained, leading to the completion of the invention.